1. Field of the Invention
The present invention relates generally to a seat suspension system for a bicycle and, more particularly, to a seat suspension system which provides superior shock absorbing characteristics while being reliably designed and low in cost to manufacture.
2. Description of the Prior Art
The standard construction of a typical low-cost bicycle includes a rigid frame supported on a pair of wheels having relatively small profile pneumatic tires. A complaint of such construction is that the bicycle is incapable of absorbing shock experienced when riding over irregular surfaces. The tires are generally capable of absorbing only minimal shock. Thus, much of the shock experienced in riding is transferred directly to the rider, which can be uncomfortable particularly when riding over extended periods of time. Moreover, many riding enthusiasts in recent times prefer to ride in off-the-road environments using a bicycle known as a mountain bike. Such riding conditions typically involve very rough terrain, and the shock experienced by the rider can be considerable.
Attempts have been made to improve bicycle riding comfort by incorporating various suspension systems in the design of the bicycle frame. Such systems may include for example, a shock absorbing rear suspension system involving pivoting rear chain stays or swing arms. However, such systems are expensive to make and add considerably to the cost of the bicycle. Thus, it is generally the case that these systems are only available in expensive, high-end bicycles. As a result, a considerable need exists for improvement in riding comfort of relatively inexpensive or low-end bicycles which are used primarily for casual pleasure riding.
Much of the shock experienced in the bicycle riding is transferred to the rider through the bicycle seat which generally supports the bulk of the rider's weight. To improve riding comfort, seats have been designed with added padding. However, such padding can interfere with the movement of the rider's thighs while pedaling, requiring extra effort on the part of the rider. Forms of seat suspension systems are known in which the seat is supported by a compression spring arrangement and suitably fitted into the seat tube of the bicycle frame such that the compression spring can absorb shocks transferred to the seat. These systems can be highly effective in improving riding comfort. One such system is disclosed, for example, in U.S. Pat. No. 5,044,648 issued Sep. 3, 1991 to Knapp.
A known disadvantage of seat suspension systems involving a seat tube compression spring arrangement is that even though these systems are less expensive than rear frame suspension systems they still are very costly to construct and are available only on expensive high-end bicycles or as a costly after-market accessory. Such known systems typically require the use of expensive materials, custom made parts and close-tolerance manufacturing techniques. This can be appreciated from reference to the aforementioned Knapp patent wherein the construction disclosed therein is seen to involve numerous metal cutting, milling and threading operations to achieve a functional product. As a consequence of their high cost, these systems are currently not used by original equipment manufacturers of relatively low-end bicycles.
Accordingly, it is desirable to provide a seat suspension system for a bicycle which is low in manufacturing cost and thus can be made available for use in low-end bicycles. Still further, it is desirable to provide such a system which is reliably designed as to function acceptably over the normal life of a bicycle.